The present invention relates to railcar coupling systems, and more particularly to draft gear assemblies used in conjunction with draft sills and couplers in railcars.
Draft gear assemblies form the connection between the couplers at the ends of adjoining railroad freight cars and the draft sills at the ends of the freight cars. The draft sills are commonly cast or fabricated sills that are mounted at the ends of the center sills of the railcar. The draft sills have a pair of front stops and a pair of rear stops, with a draft gear pocket between the stops. The draft gear assembly is received in the draft gear pocket.
Each draft gear assembly is connected to one coupler, and couplers of adjacent rail cars are connected to form the train. The train may be hundreds of cars long and drawn by one or more locomotives. Typically, there is a limited amount of slack or free movement allowed between the cars; generally there is about two (2) inches of slack. This slack permits the rail cars limited movement toward and away from each other in response to train action and yard impact events.
Train action events include, for example: locomotive start up and acceleration; dynamic braking; differences in braking forces of adjacent cars; and gravity-induced movement of the cars as the train moves onto and away from inclines. Yard impact events include xe2x80x9chumpingxe2x80x9d of the individual cars to build the train in the yard; in humping, a car is pushed over a hump in the track in the yard, released and allowed to roll down the incline of the hump toward an awaiting car; during humping, the released cars can reach speeds of 4-10 mph and can severely impact the coupler of the awaiting car.
Train action events and yard impact events both subject the couplers of the cars to buff impacts, and train action events also subject the couplers of the cars to draft impacts. These impacts are transmitted from the couplers to the draft gear assemblies to the rail car body. That is, as the couplers are pulled or pushed, the movement is translated to the freight car body through the draft gear assemblies. Typical draft gear assemblies include a yoke element that is connected to the coupler through a pin or key, a coupler follower and a draft gear, as well as other elements. Generally, the coupler follower is positioned against or closely spaced from the butt end of the coupler in the draft gear pocket, within the yoke. The draft gear is positioned between the coupler follower and the rear stops of the draft sill; other elements, such as a wedge, may be interposed between the draft gear and the coupler follower.
In buff events, the butt end of the coupler moves inward against the coupler follower toward the rear stops of the draft sill. As the coupler and coupler follower are moved rearward, the shock of the movement is transferred to the draft gear. The draft gear typically absorbs and dissipates some of the energy from this shock through friction.
In draft events, slack is taken up between adjacent cars beginning at one end of the train and ending at the other end of the train. As a result of the slack being progressively taken up, the speed differences between the railcars increases as the slack at each coupler pair is taken up, with a resultant increase in buff and draft impacts on the couplers. For instance, during locomotive acceleration of a 50 car train from rest there is a total of 100 inches of slack between the 50 pairs of couplers in the train. This slack is taken up progressively, coupler pair by coupler pair. When the 2 inch slack in the coupler pair joining the last car to the train is taken up the next to the last car may be moving at a speed of 4 miles per hour. The slack in the last coupler pair is taken up very rapidly and the last two cars are subjected to a very large impact capable of injuring the lading or the car.
Various types of draft gear assemblies have been proposed and used. Some draft gear assemblies employ mechanical springs and steel friction members held in a steel housing that is received in a yoke. Other draft gear assemblies employ elastomer springs. However, those employing a steel housing add to the weight of the railcar. Those employing elastomer springs may be difficult to install and remove from standard draft sills.
The present invention addresses the problems incident to train action and yard impact events. The present invention addresses these problems in a manner that is useful in applications such as tank cars, grain cars and coal cars, where the lading need not be protected from damage but where it is desirable to protect the railcar from damage due to train action and yard impact events. The present invention may be used in other applications as well.
In one aspect, the present invention provides a draft gear assembly for use with railcars having coupler members. The draft gear assembly has front and back ends and comprises a yoke, a coupler follower, at least one front resilient member, and at least one back resilient member. The yoke has a back wall, a top wall extending from the back wall toward the front end of the draft gear assembly, and a bottom wall extending from the back wall toward the front end of the draft gear assembly. The coupler follower is positioned between the back wall of the yoke and the front end of the draft gear assembly. The front resilient member is positioned between the coupler follower and the back wall of the yoke. The back resilient member is positioned between the yoke back wall and the back end of the draft gear assembly. The front and back resilient members are compressible. The rear follower is positioned rearward of the back resilient member. The coupler follower has a buff stroke of 4xc2xc inches but does not move in draft. The yoke has a draft stroke of 1xc2xc inches.
In another aspect, the present invention provides a draft gear assembly for use with a railcar having a coupler member and a draft sill with front and rear stops defining a draft gear pocket to receive at least part of the draft gear assembly. The draft gear pocket has a length between the front stops and rear stops. The draft gear assembly has front and back ends and comprises a yoke having a back wall, a top wall extending from the back wall toward the front end of the draft gear assembly, and a bottom wall extending from the back wall toward the front end of the draft gear assembly. The draft gear assembly also has a coupler follower positioned between the back wall of the yoke and the front end of the draft gear assembly. The coupler follower has a forward facing stop surface. The draft gear assembly has at least one front resilient member positioned between the coupler follower and the back wall of the yoke and at least one back resilient member positioned between the yoke back wall and the back end of the draft gear assembly. There is a rear follower positioned rearward of the back resilient member. The rear follower has a rearward facing stop surface. A center rod extends through the rear follower, through the back resilient member and through the back wall of the yoke. Prior to installation on the railcar the yoke, coupler follower, front resilient member, back resilient member, rear follower and center rod comprise an assembly. This assembly further includes a shortening member on the center rod at the rear follower. The length of the assembly between the stop surface of the coupler follower and the stop surface of the rear follower is less than the length of the draft gear pocket. After installation on the railcar, the coupler follower is positioned against the front stops and the rear follower is positioned against the rear stops. After installation on the railcar the yoke has a neutral position, a full draft position forward of the neutral position, and a full buff position rearward of the neutral position. The center rod is free from tension when the coupler member is in the full draft position, is free from tension and compression when the coupler member is in the neutral position, and is free from compression when the coupler member is in the full buff position.
In another aspect, the present invention provides a draft gear assembly for use with a railcar having a coupler member and a draft sill. The draft gear assembly having front and back ends and comprises a yoke, a coupler follower, a rear follower, at least one front resilient member and at least one back resilient member. The yoke has a back wall, a top wall extending from the back wall toward the front end of the draft gear assembly, a bottom wall extending from the back wall toward the front end of the draft gear assembly, and a yoke stop. The coupler follower is positioned between the back wall of the yoke and the front end of the draft gear assembly. The coupler follower has a forward facing surface positioned against the yoke stop. The front resilient member is positioned between the coupler follower and the back wall of the yoke. The back resilient member is positioned between the yoke back wall and the back end of the draft gear assembly. The rear follower is positioned rearward of the back resilient member, the rear follower having a rearward facing stop surface. The draft gear assembly also includes a center rod extending through the rear follower, through the back resilient member and through the back wall of the yoke. The draft gear assembly also includes a shortening member on the center rod at the rear follower. The distance between the rearward facing stop surface of the rear follower and the forward facing stop surface of the coupler follower is no more than 24⅝ inches.
In another aspect, the present invention provides, in combination, a draft gear assembly, a coupler and a draft sill. The draft sill has a pair of front stops and a pair of rear stops. The draft gear assembly has front and back ends and comprises a yoke having a back wall, a top wall extending from the back wall toward the front end of the draft gear assembly, and a bottom wall extending from the back wall toward the front end of the draft gear assembly. The yoke has a buff stroke from a neutral position to a full buff position and a draft stroke from the neutral position to a full draft position. The back wall of the yoke is between the front and rear stops of the draft sill. The draft gear assembly also includes a coupler follower positioned between the back wall of the yoke and the front stops of the draft sill. The coupler follower has a buff stroke from the neutral position to a full buff position. A rear follower is positioned against the rear stops of the draft sill. The yoke back wall is longitudinally spaced from the rear follower. At least one front resilient member fills the longitudinal distance between the coupler follower and the back wall of the yoke. At least one back resilient member fills the longitudinal distance between the rear follower and the back wall of the yoke. A coupler extends forward from the yoke. The coupler has a neutral position, a draft stroke from the neutral position to a full draft position forward of the neutral position and a buff stroke from the neutral position to a full buff position back from the neutral position. The coupler and yoke have draft strokes such that the distance between the front face of the yoke back wall and the coupler follower decreases from the neutral spacing when the coupler is in the full draft position and the distance between the rear face of the yoke back wall and the rear follower increases from the neutral spacing when the coupler is in the full draft position. The coupler, yoke and coupler follower have buff strokes such that the distance between the front face of the yoke back wall and the coupler follower decreases from the neutral spacing when the coupler is in the full buff position and the distance between the rear face of the yoke back wall and the rear follower decreases from the neutral spacing when the coupler is in the full buff position. The coupler draft stroke is 1xc2xc inches and the coupler buff stroke is at least 4xc2xc inches.
In another aspect, the present invention provides in combination, a draft gear assembly, a coupler and a draft sill. The draft sill has a pair of front stops and a pair of rear stops. The draft gear assembly has front and back ends and comprises a yoke having a back wall, a top wall extending from the back wall toward the front end of the draft gear assembly, and a bottom wall extending from the back wall toward the front end of the draft gear assembly. The back wall of the yoke is between the front and rear stops of the draft sill. A coupler follower is positioned between the back wall of the yoke and the front stops of the draft sill. A rear follower is longitudinally spaced from the yoke back wall. At least one front resilient member fills the longitudinal distance between the coupler follower and the back wall of the yoke. At least one back resilient member fills the longitudinal distance between the rear follower and the back wall of the yoke. A center rod extends through the rear follower, back resilient member and back wall of the yoke. A coupler extends forward from the yoke. The coupler has a neutral position, a full draft position forward of the neutral position and a full buff position back from the neutral position. The rear follower is positioned against the rear stops of the draft sill when the coupler is at the full buff position, at the full draft position and at the neutral position.